title: P2X(7) receptor antagonists display agonist-like effects on cell signaling proteins.
abstract: BACKGROUND
  The activation of various P2 receptors (P2R) by extracellular nucleotides promotes diverse cellular events, including the stimulation of cell signaling protein and increases in [Ca(2+)](i). We report that some agents that can block P2X(7)R receptors also promote diverse P2X(7)R-independent effects on cell signaling.
  
  
  METHODS
  We exposed native rat parotid acinar cells, salivary gland cell lines (Par-C10, HSY, HSG), and PC12 cells to suramin, DIDS (4,4'-diisothiocyano stilbene-2,2'-disulfonic acid), Cibacron Blue 3GA, Brilliant Blue G, and the P2X(7)R-selective antagonist A438079, and examined the activation/phosphorylation of ERK1/2, PKCδ, Src, CDCP1, and other signaling proteins.
  
  
  RESULTS
  With the exception of suramin, these agents blocked the phosphorylation of ERK1/2 by BzATP in rat parotid acinar cells; but higher concentrations of suramin blocked ATP-stimulated (45)Ca(2+) entry. Aside from A438079, these agents increased the phosphorylation of ERK1/2, Src, PKCδ, and other proteins (including Dok-1) within minutes in an agent- and cell type-specific manner in the absence of a P2X(7)R ligand. The stimulatory effect of these compounds on the tyrosine phosphorylation of CDCP1 and its Src-dependent association with PKCδ was blocked by knockdown of CDCP1, which also blocked Src and PKCδ phosphorylation.
  
  
  CONCLUSIONS
  Several agents used as P2X(7)R blockers promote the activation of various signaling proteins and thereby act more like receptor agonists than antagonists.
  
  
  CONCLUSIONS
  Some compounds used to block P2 receptors have complicated effects that may confound their use in blocking receptor activation and other biological processes for which they are employed, including their use as blockers of various ion transport proteins.
authors.affiliation: Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA.
authors.forename: Lee
authors.initials: L
authors.lastname: Hedden
authors.forename: Cyril H
authors.initials: CH
authors.lastname: Benes
authors.forename: Stephen P
authors.initials: SP
authors.lastname: Soltoff
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000818:Animals; D000951:Antigens, Neoplasm / Q000235:genetics / Q000378:metabolism; D015153:Blotting, Western; D002460:Cell Line; D002478:Cells, Cultured; D006801:Humans; D008297:Male; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D016716:PC12 Cells; D010766:Phosphorylation / Q000187:drug effects; D051745:Protein Kinase C-delta / Q000378:metabolism; D011506:Proteins / Q000378:metabolism*; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000378:metabolism; D058911:Purinergic P2X Receptor Agonists / Q000494:pharmacology*; D058920:Purinergic P2X Receptor Antagonists / Q000494:pharmacology*; D034622:RNA Interference; D051381:Rats; D017207:Rats, Sprague-Dawley; D058486:Receptors, Purinergic P2X7 / Q000378:metabolism*; D012394:Rosaniline Dyes / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects*; D013498:Suramin / Q000494:pharmacology; D014227:Triazines / Q000494:pharmacology
chemical_list: D000951:Antigens, Neoplasm; C558930:CDCP1 protein, rat; D011506:Proteins; D058911:Purinergic P2X Receptor Agonists; D058920:Purinergic P2X Receptor Antagonists; D058486:Receptors, Purinergic P2X7; D012394:Rosaniline Dyes; D014227:Triazines; C012842:Cibacron Blue F 3GA; D013498:Suramin; D016392:Proto-Oncogene Proteins pp60(c-src); D051745:Protein Kinase C-delta; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; C004692:coomassie Brilliant Blue; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid